Metallic glass alloys are a class of metal materials that are characterized by their disordered atomic-scale structure in spite of their metallic constituent elements. By comparison, conventional metallic materials typically possess a highly ordered atomic structure. Metallic glass alloys typically possess a number of useful material properties that render them highly effective as engineering materials. For example, metallic glass alloys are generally much harder than conventional metals, and are generally tougher than ceramic materials. In addition, metallic glass alloys are relatively corrosion resistant and unlike conventional glass materials can have good electrical conductivity. The manufacture of metallic glass materials is compatible with relatively simple forming processes, such as injection molding.
Early metallic glass alloys required cooling rates on the order of 106 K/s to remain amorphous, and were thereby limited in the thickness with which they could be formed. More recently, additional metallic glass alloys that are more resistant to crystallization can form metallic glasses at much lower cooling rates, and can therefore be made to be much thicker. These thicker metallic glasses are known as ‘bulk metallic glasses” (“BMGs”).
Some Zr-based BMG alloys may include small amounts of Hf, but little empirical data exists to describe the effect of Hf on the material properties of BMG alloys. In the context of Zr-based BMG alloys, the inclusion of Hf may indeed enhance material properties such as elastic modulus and yield strength.